Semiconductor junction profile and method for the production thereof

Abstract

A planar slice ( 1 ) of semiconductor substrate material of a first conductivity type is provided on one face with a first region ( 13 a ) of a second conductivity type having a higher dopant concentration than that of the substrate and on the opposite face a second region ( 13 b ) of said second conductivity type having a higher dopant concentration than that of the substrate. Each of the faces has had removed from part of it a depth of material which increases gradually as the outer edge is approached so that the junction between each of the regions ( 13 a , 13 b ) and the substrate is exposed along a path following the shape of the perimeter of the slice but so that the removal of material ceases at a distance outwardly beyond the exposure of the junction to leave a rim ( 11 ) of the original planar faces of the slice at its perimeter.

What is claimed is:  
     
         1 . A planar slice of semiconductor substrate material of a first conductivity type provided at one face with a first region of a second conductivity type having a higher dopant concentration than that of the substrate and at the opposite face a second region of said second conductivity type having a higher dopant concentration than that of the substrate, wherein each of said faces has had removed from part of it by abrasion a depth of material which increases gradually as the outer edge is approached so that the junction between each of said regions and the substrate is exposed along a path following the shape of the perimeter of the slice but so that the removal of material ceases at a distance outwardly beyond the exposure of the junction to leave a rim of the original planar faces of the slice at its perimeter.  
     
     
         2 . A slice according to    claim 1   , wherein the slice is a disc.  
     
     
         3 . A slice according to    claim 1   , wherein the material of the slice is silicon.  
     
     
         4 . A slice according to    claim 1   , wherein the edge of the slice is rounded in section.  
     
     
         5 . A slice according to    claim 1   , wherein said first and second regions of said second conductivity type are formed by the diffusion of a dopant of said second conductivity type into the faces of the substrate so as to over-dope the original first conductivity type and form a junction therewith at a predetermined depth.  
     
     
         6 . A slice according to    claim 1   , wherein said first and second regions of said second conductivity type extend around the outer edge of the slice to form a surface region which is broken only where each of said junctions is exposed.  
     
     
         7 . A slice according to    claim 1   , wherein the gradual increase in depth of the removal of material constitutes an angle of less than 7° relative to the plane of the junction thereby exposed.  
     
     
         8 . A slice according to    claim 7   , wherein said angle is in the range from 2° to 5°.  
     
     
         9 . A slice according to    claim 7   , wherein said angle is about 3°.  
     
     
         10 . A slice according to    claim 1   , wherein the substrate material is of n-type conductivity and the surface regions are of p-type conductivity.  
     
     
         11 . A slice according to    claim 1    with the addition of further semiconductor regions and ohmically connected electrodes so as to form an operable electrical device.  
     
     
         12 . A method of producing a semiconductor junction profile, comprising providing a planar slice of semiconductor substrate material of a first conductivity type provided at one face with a first region of a second conductivity type having a higher dopant concentration than that of the substrate and at the opposite face a second region of said second conductivity type, having a higher dopant concentration than that of the substrate, the method comprising removing from part of each of said faces by abrasion a depth of material which increases gradually as the outer edge is approached so that the junction between each of said regions and the substrate is exposed along a path following the shape of the perimeter of the slice but so that the removal of material ceases at a distance outwardly beyond the exposure of the junction to leave a rim of the original planar faces of the slice at its perimeter.  
     
     
         13 . A method according to    claim 12   , wherein the slice is a disc.  
     
     
         14 . A method according to    claim 12   , wherein the material of the slice is silicon.  
     
     
         15 . A method according to    claim 12   , wherein the edge of the slice is rounded in section.  
     
     
         16 . A method according to    claim 12   , wherein said first and second regions of said second conductivity type are formed by the diffusion of a dopant of said second conductivity type into the faces of the substrate so as to over-dope the original first conductivity type and form a junction therewith at a predetermined depth.  
     
     
         17 . A method according to    claim 12   , wherein said first and second regions of said second conductivity type extend around the outer edge of the slice to form a surface region which is broken only where each of said junctions is exposed.  
     
     
         18 . A method according to    claim 12   , wherein the gradual increase in depth of the removal of material constitutes an angle of less than 7° relative to the plane of the junction thereby exposed.  
     
     
         19 . A method according to    claim 18   , wherein said angle is in the range from 2° to 5°.  
     
     
         20 . A method according to    claim 18   , wherein said angle is about 3°.  
     
     
         21 . A method according to    claim 12   , wherein the substrate material is of n-type conductivity and the surface regions are of p-type conductivity.